In an electric vehicle, a number of batteries are typically grouped together and mounted in a battery tray. The tray is covered with a protective housing and this entire assembly containing the batteries is provided outside the passenger compartment on the floor of vehicle. A plurality of holes for allowing air to enter the battery tray are formed at specific locations of the same.
The batteries used in an electric vehicle must be recharged after the vehicle has been driven a certain distance, which varies from vehicle to vehicle. Recharging is performed using normal charging or quick charging. Heat develops by the chemical reactions taking place inside the batteries during charging, and ideally, the temperature of the batteries is maintained in the range of 25˜30° C. However, when actually performing normal or quick charging, the temperature of the batteries far exceeds this desirable level. Further, the ideal temperature of 25˜30° C. is not possible to maintain when the outside temperature itself surpasses this range of temperatures. This is the case even when a cooling fan is used to expel the air from within the battery tray during recharging. Overheating is therefore a problem when recharging the batteries for an electric vehicle.
The problem of overheating reduces battery performance and battery life. If the batteries are severely overheated, the batteries may deform so that a short develops internally. This may result in vaporized battery gas combusting or exploding, thereby potentially causing the vehicle to catch fire.
To remedy this problem, cooling systems using an air conditioner have been employed. However, while providing sufficient cooling, such systems have a drawback in that condensation in the battery tray as a result of the air conditioner can cause corrosion in the batteries and wiring. Also, the presence of condensation water can degrade the overall performance or cause short circuits.
To address the condensation problem, one or more drain holes may be placed in the bottom of the battery tray. However, due to the forced air flow of cooling air through the battery tray, a negative pressure can be formed that prevents complete draining of the condensation water. Thus, condensation water can accumulate in the battery tray in spite of the drain holes.